Best seam sealer ? Good or bad ?

[JohnT]

Ok. I'm in the middle of a rebuild . I have the front fenders off and noticed that there is a lot of seams around the front cowling where the factory put seam sealer on and it's starting to peel . Should sand blast everything clean and replace with seam sealer ? Or is it a better idea to clean and repair with a bed liner like Hercule liner ?Or maybe POR 15? What your thoughts ?

 

[ep67bro]

Scrape off the loose stuff prime with PRO 15 or some other rust paint and then reapply the seam sealer. It is cheap you can get it from NAPA.

 

[nrramse]

A few years ago, a body shop guy told me to avoid using silicone caulk because it causes iron to rust. It sounds like you're avoiding that anyways, but it seemed like a good place to mention it anyhow.

Newell

 

[00gyrhed]

Yes cilcone can make stell rust. Also if you think you are ever going to repaint the silcone will cause fisheyes and it can be almost impossible to get it all out.

I have been using 3m fast and firm but it will crack sometimes. especially if the seam vibrates or is stressed. I have also used the 3M flexible seam sealer it never really hardens but it gets pretty tough especialy when painted over.

There are bug differences in seam sealer. I have been told to stick with 3M or Fusor seam sealers, nut I don't have any experience with anything other than 3M.

 

[JohnT]

I thought that seam sealer had to go on bare steel ? I didn't know that about silicone caulking . Thanks for that little tid bit . To be total honest the seam sealer was the Bronco big down fall , every seam on the truck has seam sealer in it , and as soon as it cracks it let mositure in and rust starts . Thats why I was asking ahead time .

 

[Madgyver]

Not sure what is happening with Duramix but their stuff are good....

http://www.levineautoparts.com/ducoflsese.html

 

[allenfahey]

I thought that seam sealer had to go on bare steel ? I didn't know that about silicone caulking . Thanks for that little tid bit . To be total honest the seam sealer was the Bronco big down fall , every seam on the truck has seam sealer in it , and as soon as it cracks it let mositure in and rust starts . Thats why I was asking ahead time .

You don't want to put seam sealer on bare steel. Use primer, sand and scuff, and before you are ready for paint put on your seam sealer. After it dries apply the paint right over it. Fusor 800 seam sealer is a good seam sealer that is easy to apply. You can apply paint right overtop of it after 30 minutes and remains flexible. Duramix and SEM also makes good seam sealers but you need a special $$$$ double barrel gun to apply it. The Fusor uses a regular caulking gun.

 

[Casey835]

From what I understand POR 15 makes a seam sealer-I was planning to check that out!

 

[JohnT]

Thanks Guys for all of information!

 

[firehawk]

Do not use 3M Fast and firm. That stuff is the worst I have ever used.

I recommend a urethane seam sealer as it remains flexible. I used a two part and it gets hard and can crack, not nearly as bad as the fast and firm but it will crack as it did in the seams between the quarters and rockers at the bottom.

 

[JohnT]

I went to auto body store they suggested a seam sealer named Flexiclear , It's made by 3M and it's suppose stay soft . It's was only 16 dollars a tube ,And you can use it with a regular caulking gun .I'm going to give it a try . The guys also suggested cleaning the surface do to bare metal and use a good primer then apply the seam sealer , then paint with the rest of the body .

 

[needabronco]

I used the 3M Fast and Firm. It does shrink back a little bit, and I did have to touch up a couple of spots afterwords, but it's not a big deal. I applied seam sealer then primed/sealed. So touching it up before paint wasn't a big deal. I could see how it would be a big deal if I painted right over it...

On my Bronco there really wasn't very much seam sealer on the bottom of the tub. I did seam seal where I patched in the floors, and did everything else on the tub, doors, and tailgate and used about a tube and a half.

One trick is to apply the seam sealer and then wipe it smooth with a finger that is wet with wax and grease remover. The wax and grease remover helps smooth out the seam sealer without making a goopey sticky mess.

 

[gumbydood]

Either sikaflex or 3M5200 marine adhesive/sealant. Great stuff, sticks to anything, remains flexible, can be sanded, painted etc. Available in standard or large caulking tube. Local lumber store sells for about $6/tube. Designed for installing portholes/etc through boat hulls.
I learned about it while working for a guy who modified passenger vans for transit use. We used it like bondo where we extended the door openings, sealed the gaps between the flooring and the wheelchair tie-down strips, sealed around the window openings in the fiberglass roofs we installed, and sealed the seam between the original metal roof and the fiberglass caps.

I built a camper van in 2001, putting a fiberglass roof onto the original van roof, and sealed the seam with the 3M5200. I've put about 35K miles (?) on it, in everything from subzero to over 100 degree temps, on roads and trails (no hardcore off-road stuff) and there are no signs of separation at any of the seams.

Good luck,
G'dood

 

[Fishbone]

Lot's of seam sealers out there, and I'm sure several are good, but I have had very good luck with this one: http://www.eastwood.com/seam-sealer-black-ultra-flex.html

I haven't seen it crack yet, although anything will fail eventually. I would warn that you need to get it right the first time because it's like rubber when it dries. That's a good thing, but despite their claims, it's not really sandable. It also acts as an adheisive. If you can lay down a nice bead without tooling or wiping it... you'll like this stuff.

 

[myclsic69]

I wonder if the same seam sealer will work on the body seam were the tail peice and the rear Quarter join?

 

[Evian]

You can use silicone to seal the corner only if you POR-15 first top and bottom allow it to dry for 4-5 days then silicone it. Silicone will make metal rust but if it is coded with POR-15 first it won't. I did this to my CJ7 seven years ago and the rust hasn't shown it ugly head.